TY - JOUR A1 - Abbott, Joshua L. A1 - Straube, Arthur A1 - Aarts, Dirk G. A. L. A1 - Dullens, Roel P. A. T1 - Transport of a colloidal particle driven across a temporally oscillating optical potential energy landscape JF - New J. Phys. N2 - A colloidal particle is driven across a temporally oscillating one-dimensional optical potential energy landscape and its particle motion is analysed. Different modes of dynamic mode locking are observed and are confirmed with the use of phase portraits. The effect of the oscillation frequency on the mode locked step width is addressed and the results are discussed in light of a high-frequency theory and compared to simulations. Furthermore, the influence of the coupling between the particle and the optical landscape on mode locking is probed by increasing the maximum depth of the optical landscape. Stronger coupling is seen to increase the width of mode locked steps. Finally, transport across the temporally oscillating landscape is studied by measuring the effective diffusion coefficient of a mobile particle, which is seen to be highly sensitive to the driving velocity and mode locking. Y1 - 2019 U6 - https://doi.org/10.1088/1367-2630/ab3765 VL - 21 SP - 083027 ER - TY - JOUR A1 - Boniface, Dolachai A1 - Straube, Arthur A1 - Tierno, Pietro T1 - Photocatalytic magnetic microgyroscopes with activity-tunable precessional dynamics JF - Nano Letters N2 - Magnetic nano/microrotors are passive elements that spin around an axis due to an external rotating field while remaining confined to a close plane. They have been used to date in different applications related to fluid mixing, drug delivery or biomedicine. Here we realize an active version of a magnetic microgyroscope which is simultaneously driven by a photo-activated catalytic reaction and a rotating magnetic field. We investigate the uplift dynamics of this colloidal spinner when it stands up and precesses around its long axis while self-propelling due to the light induced decomposition of hydrogen peroxide in water. By combining experiments with theory, we show that activity emerging from the cooperative action of phoretic and osmotic forces effectively increase the gravitational torque which counteracts the magnetic and viscous ones, and carefully measure its contribution. Y1 - 2024 U6 - https://doi.org/10.1021/acs.nanolett.4c03386 VL - 24 IS - 47 SP - 14950 EP - 14956 ER - TY - JOUR A1 - Cereceda-López, Eric A1 - Ostinato, Mattia A1 - Ortiz-Ambriz, Antonio A1 - Straube, Arthur A1 - Palassini, Matteo A1 - Tierno, Pietro T1 - Excluded volume induces buckling in optically driven colloidal rings JF - Phys. Rev. Research N2 - In our combined experimental, theoretical and numerical work, we study the out of equilibrium deformations in a shrinking ring of optically trapped, interacting colloidal particles. Steerable optical tweezers are used to confine dielectric microparticles along a circle of discrete harmonic potential wells, and to reduce the ring radius at a controlled quench speed. We show that excluded-volume interactions are enough to induce particle sliding from their equilibrium positions and nonequilibrium zigzag roughening of the colloidal structure. Our work unveils the underlying mechanism of interfacial deformation in radially driven microscopic discrete rings. Y1 - 2024 U6 - https://doi.org/10.1103/PhysRevResearch.6.L012044 VL - 6 SP - L012044 ER - TY - JOUR A1 - del Razo, Mauricio A1 - Frömberg, Daniela A1 - Straube, Arthur A1 - Schütte, Christof A1 - Höfling, Felix A1 - Winkelmann, Stefanie T1 - A probabilistic framework for particle-based reaction–diffusion dynamics using classical Fock space representations JF - Letters in Mathematical Physics Y1 - 2022 U6 - https://doi.org/10.1007/s11005-022-01539-w VL - 112 IS - 49 ER - TY - JOUR A1 - Höfling, Felix A1 - Straube, Arthur T1 - Langevin equations and a geometric integration scheme for the overdamped limit of rotational Brownian motion of axisymmetric particles JF - Physical Review Research N2 - The translational motion of anisotropic or self-propelled colloidal particles is closely linked with the particle’s orientation and its rotational Brownian motion. In the overdamped limit, the stochastic evolution of the orientation vector follows a diffusion process on the unit sphere and is characterized by an orientation-dependent (“multiplicative”) noise. As a consequence, the corresponding Langevin equation attains different forms depending on whether Itō’s or Stratonovich’s stochastic calculus is used. We clarify that both forms are equivalent and derive them in a top-down approach from a geometric construction of Brownian motion on the unit sphere, based on infinitesimal random rotations. Our approach suggests further a geometric integration scheme for rotational Brownian motion, which preserves the normalization constraint of the orientation vector exactly. We show that a simple implementation of the scheme, using Gaussian random rotations, converges weakly at order 1 of the integration time step, and we outline an advanced variant of the scheme that is weakly exact for an arbitrarily large time step. Due to a favorable prefactor of the discretization error, already the Gaussian scheme allows for integration time steps that are one order of magnitude larger compared to a commonly used algorithm for rotational Brownian dynamics simulations based on projection on the constraining manifold. For torques originating from constant external fields, we prove by virtue of the Fokker-Planck equation that the constructed diffusion process satisfies detailed balance and converges to the correct equilibrium distribution. The analysis is restricted to time-homogeneous rotational Brownian motion (i.e., a single rotational diffusion constant), which is relevant for axisymmetric particles and also chemically anisotropic spheres, such as self-propelled Janus particles. Y1 - 2025 U6 - https://doi.org/10.1103/wzdn-29p4 VL - 7 SP - 043034 ER - TY - JOUR A1 - Kourov, Mikhail N. A1 - Samoilova, Anna E. A1 - Straube, Arthur T1 - Dynamics of a chain of interacting magnetic particles in a one-dimensional periodic energy landscape JF - Bull. Russ. Acad. Sci. Phys. N2 - We explore the dynamics of a one-dimensional chain of paramagnetic colloidal particles in a periodic potential. The model accounts for a constant external force, along with magnetic dipolar attraction and hard-core repulsive interactions between particles. Numerical simulations reveal the emergence of a traveling kink – a chain defect propagating along the chain. We show that the kink emerges beyond a critical force threshold and identify parameter regimes corresponding to distinct dynamic modes such as a pinned kink, a running kink, a cluster kink, and chain drift. Y1 - 2025 U6 - https://doi.org/10.1134/S1062873825711742 SN - 1062-8738 VL - 89 IS - 7 SP - 1086 EP - 1092 ER - TY - JOUR A1 - Stoop, Ralph L. A1 - Straube, Arthur A1 - Johansen, Tom H. A1 - Tierno, Pietro T1 - Collective directional locking of colloidal monolayers on a periodic substrate JF - Phys. Rev. Lett. N2 - We investigate the directional locking effects that arise when a monolayer of paramagnetic colloidal particles is driven across a triangular lattice of magnetic bubbles. We use an external rotating magnetic field to generate a two-dimensional traveling wave ratchet forcing the transport of particles along a direction that intersects two crystallographic axes of the lattice. We find that, while single particles show no preferred direction, collective effects induce transversal current and directional locking at high density via a spontaneous symmetry breaking. The colloidal current may be polarized via an additional bias field that makes one transport direction energetically preferred. Y1 - 2020 U6 - https://doi.org/10.1103/PhysRevLett.124.058002 VL - 124 SP - 058002 ER - TY - JOUR A1 - Straube, Arthur A1 - Höfling, Felix T1 - Memory effects in colloidal motion under confinement and driving JF - J. Phys. A: Math. Theor. N2 - The transport of individual particles in inhomogeneous environments is complex and exhibits non-Markovian responses. The latter may be quantified by a memory function within the framework of the linear generalised Langevin equation (GLE). Here, we exemplify the implications of steady driving on the memory function of a colloidal model system for Brownian motion in a corrugated potential landscape, specifically, for one-dimensional motion in a sinusoidal potential. To this end, we consider the overdamped limit of the GLE, which is facilitated by separating the memory function into a singular (Markovian) and a regular (non-Markovian) part. Relying on exact solutions for the investigated model, we show that the random force entering the GLE must display a bias far from equilibrium, which corroborates a recent general prediction. Based on data for the mean-square displacement (MSD) obtained from Brownian dynamics simulations, we estimate the memory function for different driving strengths and show that already moderate driving accelerates the decay of the memory function by several orders of magnitude in time. We find that the memory may persist on much longer timescales than expected from the convergence of the MSD to its long-time asymptote. Furthermore, the functional form of the memory function changes from a monotonic decay to a non-monotonic, damped oscillatory behaviour, which can be understood from a competition of confined motion and depinning. Our analysis of the simulation data further reveals a pronounced non-Gaussianity, which questions the Gaussian approximation of the random force entering the GLE. Y1 - 2024 U6 - https://doi.org/10.1088/1751-8121/ad5b2d SN - 1751-8113 VL - 57 SP - 295003 PB - IOP Publishing ER - TY - JOUR A1 - Straube, Arthur A1 - Höfling, Felix T1 - Depinning transition of self-propelled particles JF - Physical Review E N2 - For self-propelled particles in a corrugated potential landscape, we describe a discontinuous change of the classical depinning transition and a host of unique behaviors sensitive to the persistence of the propulsion direction. Exact and semianalytic results for active Brownian particles corroborate a creep regime with a superexponentially suppressed drift velocity upon lowering the force towards the threshold value. This unusual nonlinear response emerges from the competition of two critical scaling laws with exponents of 1/2 for rapidly reorienting particles and 𝑑/2 for particles with a persistent orientation; the latter case depends on the dimensionality 𝑑 of rotational motion and also includes run-and-tumble particles. Additionally, different giant diffusion phenomena occur in the two regimes. Our findings extend to random dynamics with bounded noise near a saddle-node bifurcation and have potential applications in various nonequilibrium problems, including arrested active matter and cell migration. Y1 - 2024 U6 - https://doi.org/10.1103/PhysRevE.110.L062601 VL - 110 IS - 6 SP - L062601 ER - TY - JOUR A1 - Straube, Arthur A1 - Kowalik, Bartosz G. A1 - Netz, Roland R. A1 - Höfling, Felix T1 - Rapid onset of molecular friction in liquids bridging between the atomistic and hydrodynamic pictures JF - Commun. Phys. N2 - Friction in liquids arises from conservative forces between molecules and atoms. Although the hydrodynamics at the nanoscale is subject of intense research and despite the enormous interest in the non-Markovian dynamics of single molecules and solutes, the onset of friction from the atomistic scale so far could not be demonstrated. Here, we fill this gap based on frequency-resolved friction data from high-precision simulations of three prototypical liquids, including water. Combining with theory, we show that friction in liquids emerges abruptly at a characteristic frequency, beyond which viscous liquids appear as non-dissipative, elastic solids. Concomitantly, the molecules experience Brownian forces that display persistent correlations. A critical test of the generalised Stokes–Einstein relation, mapping the friction of single molecules to the visco-elastic response of the macroscopic sample, disproves the relation for Newtonian fluids, but substantiates it exemplarily for water and a moderately supercooled liquid. The employed approach is suitable to yield insights into vitrification mechanisms and the intriguing mechanical properties of soft materials. Y1 - 2020 U6 - https://doi.org/10.1038/s42005-020-0389-0 VL - 3 SP - 126 PB - Nature ER -